Hydraulic camshaft adjuster and method for operating the same

ABSTRACT

A hydraulic camshaft adjuster for adjusting the angle of rotation of the camshaft of an internal combustion engine relative to its crankshaft, including an external rotor connected in a rotationally fixed manner to a driving wheel, and an internal rotor connected in a rotationally fixed manner to a driving wheel, and an internal rotor connected in a rotationally fixed manner to a camshaft, the external rotor having at least one hydraulic chamber with radial partitions and two side walls, and the internal rotor having a hub with at least one hydraulically swiveling blade which divides the hydraulic chamber into two working chambers operated by oil pressure which is controlled by an electronic regulator via a control valve. The swiveling blade having, between stops, a base position which can be locked by pins in grooves.

FIELD OF THE INVENTION

[0001] The invention relates to a hydraulic camshaft adjuster for adjusting the angle of rotation of the camshaft of an internal combustion engine relative to its crankshaft, in particular according to the preamble of independent device claim 1 and of independent method claim 10.

SUMMARY OF THE INVENTION

[0002] For thermodynamic reasons, it is expedient, in the case of certain concepts of engines, to be able to make an adjustment both toward “leading” and toward “trailing” from a base position, which is locked during starting of the engine. This means locking the camshaft adjuster between the leading stop and trailing stop.

[0003] DE 199 18 910 A1 discloses a hydraulic camshaft adjuster for adjusting the angle of rotation of the camshaft of an internal combustion engine relative to its crankshaft, which camshaft adjuster has an external rotor connected in a rotationally fixed manner to a driving wheel, and an internal rotor connected in a rotationally fixed manner to the camshaft, the external rotor having at least one hydraulic chamber with radial partitions and two side walls, and the internal rotor having a hub with at least one swiveling blade which divides the hydraulic chamber into two working chambers in an oil-tight manner. The internal rotor can be swiveled hydraulically between a trailing stop and a leading stop by an oil pressure which is controlled by an electronic regulator via a control valve, and has, between the stops, a base or central position which can be locked by two spring-loaded and hydraulically unlockable locking pins.

[0004] The two locking pins in the above publication are arranged radially. They are therefore subject, during operation of the engine, to the centrifugal force which is directed counter to the spring force and jeopardizes the latter. It is also disadvantageous that the main locking pin blocks the presetting and restoring directions of the internal rotor while the second locking pin is designed, as it were, as an intercepting pin for the internal rotor, which pin enables the main locking pin to be latched in place and once more blocks one of the directions of rotation of the internal rotor. In this case, an extremely precise arrangement of the two pins with respect to each other is required in order to ensure secure locking. In addition, the production of the mating contour to the intercepting pin is associated with considerable manufacturing costs.

OBJECT OF THE INVENTION

[0005] The invention is therefore based on the object of enabling the internal rotor of a hydraulic camshaft adjuster to be locked in a functionally reliable and low-wearing manner in a base position lying between its leading stop and trailing stop and of keeping the structural outlay required for this as low as possible.

SUMMARY OF THE INVENTION

[0006] The object is achieved according to the invention by the features of independent device claim 1. The locking pins, which are preferably of identical design, are cost-effective to manufacture. Since the latter are situated in the hub of the internal rotor, the blades thereof can be designed as cost-effective, flat swiveling blades which are guided in radial grooves in the hub. The two locking pins are likewise arranged in the hub parallel to its axis of rotation, so that the centrifugal force can only act perpendicularly with respect to the pin axes and thereby only has a marginal effect on the functioning thereof.

[0007] Since the locking pins can be latched into locking grooves instead of into locking bores, the locking and unlocking thereof is simplified and is associated with less stress on and wear of the locking edges.

[0008] The design of the locking grooves in the shape of a circular arc is required in order to be able to swivel the internal rotor using locking pins which have been latched in place. If the locking grooves, and therefore also the axis of the locking pins, lie on a common circle about the rotational axis of the internal rotor, advantages are produced during the manufacturing of locking grooves and guide bores of the locking pins.

[0009] In principle, the locking pins and, as a result of them, the locking grooves can be arranged at any desired points of the hub or of the side walls. In addition to manufacturing aspects, the functionally correct supplying of compressed oil to the working chambers and to the locking pins is important here.

[0010] The semicircular ends of the locking grooves can likewise be manufactured precisely with little outlay. The required width of the locking groove is produced here from the diameter of the locking pins and the required clearance of the same in the locking grooves.

[0011] It is advantageous for one of the ends of the two locking grooves to be designed as a central stop for the locking pins, for fixing the central position of the swiveling blades. In this manner, locking grooves and central stops can be manufactured in one working step.

[0012] Since the central stops are arranged mirror-symmetrically, each central stop blocks a different swiveling direction. As a result, the stress on and wear of the central stops are minimized.

[0013] One advantageous design of the invention consists in those ends of the two locking grooves which are remote from the stop being arranged, when the swiveling blades bear against the leading stop and trailing stop, at a distance from the locking pins which are each latched in place. This ensures that the leading and the trailing stops are only used for the swiveling blades, and the central stops are used only for the locking pins.

[0014] For a cost-effective installation and adjustment of the camshaft adjuster, it is advantageous if the central stops can be set with respect to the leading and trailing stops by rotation of the first side wall, which is provided with the locking grooves, relative to the external rotor.

[0015] For a functionally correct latching in place and unlatching of the locking pins, it is important for the locking grooves and their oil channels to be flow-connected to the corresponding working chambers via oil lines which are preferably arranged in the first side wall. It is also conceivable to branch off the oil lines from the oil pressure lines in the hub and to connect them to corresponding bores in the locking pins.

[0016] If the locking grooves are in each case arranged in different side walls, the angular position of the central stops of the two locking pins can be set independently of each other.

[0017] The object of the invention is also achieved by the features of method claim 10, the electronic regulator regulating the oil pressure in the working chambers during the shutting off and restarting of the internal combustion engine in such a way that, with additional use of the dragging torque of the camshaft, the starting of the engine takes place from a base or central position of the swiveling blades, which position is locked by the two locking pins.

[0018] For a regulated switching off and a low-noise petering out of the internal combustion engine, it is advantageous that at low idling of the internal combustion engine before it is shut off, the electronic regulator charges, with a control valve switched to be de-energized, the first working chamber together with associated first locking groove with oil pressure, as a result of which the first locking pin is unlocked and the swiveling blades come to bear against the leading stop while the second locking pin, with the second working chamber unpressurized, is outside the second locking groove and is prestressed by its compression spring.

[0019] It is advantageous that, with the internal combustion engine at a standstill and, as a result, an absence of oil pressure, the first locking pin is latched in place in the first locking groove and the swiveling blades have a swiveling position between the leading stop and the base position while the second locking pin is also arranged outside the second locking groove and is prestressed by its compression spring.

[0020] For reliable starting of the engine, it is advantageous that, when the internal combustion engine is started, the internal rotor is adjusted to “trailing” by the dragging torque of the camshaft until the first locking pin in the first locking groove comes against the first central stop and thereby enables the second locking pin to latch into the second central stop of the second locking groove, so that the starting of the engine takes place with the central position completely locked.

[0021] For the running-up of the internal combustion engine, advantages are provided if, directly after starting of the engine has taken place, the regulator raises the oil pressure in the first oil pressure lines, the first working chambers and the first locking groove, thereby unlocking the first locking pin and keeping the second locking pin in pressure contact with the second central stop. As an alternative, the regulator can also raise the oil pressure in the second oil pressure lines, the second working chambers and the second locking groove, as a result of which the second locking pin is unlocked and the first locking pin remains in pressure contact with the first central stop.

[0022] If, in order to transfer to regulated operation, the regulator adjusts the swiveling blades into the region in front of the trailing stop, by means of a higher pressure in the second working chamber than in the first working chamber, and thereby also unlocks the second locking pin, the internal rotor can move freely and transfer into regulated operation.

[0023] It may also be advantageous if the camshaft adjuster has a spring which assists the rotation of the internal rotor toward “leading” or “trailing” as the internal combustion engine peters out. A spring of this type may be designed, for example, as a helical torsion spring or as a spiral spring which is arranged within or outside the camshaft adjuster.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Further features of the invention emerge from the following description and the drawings in which an exemplary embodiment of the invention is illustrated schematically. In the drawings:

[0025]FIG. 1 shows a cross section through a camshaft adjuster which is designed according to the invention and is locked in the central position;

[0026]FIG. 2 shows a detailed section A-A according to FIG. 1 through a locking pin;

[0027]FIG. 3 shows a cross section according to FIG. 1, but with swiveling blades bearing against the trailing stop;

[0028]FIG. 4 shows a cross section according to FIG. 1, but with swiveling blades bearing against the leading stop.

DETAILED DESCRIPTION OF THE DRAWINGS

[0029]FIG. 1 shows a cross section through a hydraulic camshaft adjuster designed according to the invention. Said camshaft adjuster has a cylindrical external rotor 1 and a coaxial internal rotor 2 which, as emerges from FIG. 2, are bounded axially by a first side wall 10 and a second side wall 11. The direction of rotation of the camshaft adjuster is indicated by an arrow.

[0030] The external rotor 1 bears a chain wheel (not illustrated) which connects it in a rotationally fixed manner via a chain to a crankshaft of an internal combustion engine. The chain, the crankshaft and the internal combustion engine itself are likewise not illustrated in the drawings. The external rotor 1 has, on its internal circumference, four radial partitions 3 which bound four hydraulic chambers 4.

[0031] The internal rotor 2 is connected in a rotationally fixed manner to a camshaft (not illustrated) by a central clamping screw (not illustrated). Said internal rotor has a cylindrical hub 5 having four radial slots 6 into which four swiveling blades 7 can be inserted. The latter bring about an oil-tight division of the hydraulic chambers 4 into first working chambers 8 and second working chambers 9. The hydraulic chambers 4 and the first and second working chambers 8, 9 are bounded toward the rotational or swiveling axis 12 by the hub 5 which, together with the tips 13 of the radial partitions 3, forms gap seals between the working chambers 8 and 9.

[0032] The first and second working chambers 8, 9 are supplied with compressed oil through first and second compressed oil lines 14, 15 in the hub 5. The compressed oil passes via a rotary oil leadthrough (not illustrated) into a first and a second axial oil bore 16, 17, the second axial oil bore 17 being provided at the same time as a passage bore for the central clamping screw (not illustrated). The first and second compressed oil lines 14, 15 are also used for conducting away the unpressurized oil into the oil sump (not illustrated).

[0033] An electronic regulator (not illustrated), which controls a control valve (not illustrated), is used for controlling the two oil flows. By appropriate influencing of the two oil flows, the swiveling blades 7 can be swiveled to and fro between the leading and trailing stops 18, 19, which are situated on the partitions 3. In addition, a central position of the swiveling blades 7 is provided for the starting of the internal combustion engine, said central position providing thermodynamic advantages in the case of certain concepts of the engine.

[0034] A first and second locking pin 20, 21 (see also FIG. 2) are used for locking the swiveling blades 7 in their central position. Said locking pins are of identical design and are guided in axially parallel bores 22 in the hub 5. Compression springs 23 are situated in the locking pins 20, 21, which are hollow at least on one side, said compression springs pressurizing the locking pins 20, 21 and the bearing cups 24 arranged in the axis of said pins. During swiveling of the internal rotor 2, the bearing cups 24 facilitate the sliding of the compression springs 23 along the inside of the second side wall 11.

[0035] A first locking groove 25 for the first locking pin 20 and a second locking groove 26 for the second locking pin 21 are provided in the first side wall 10. The locking grooves 25, 26 are designed in the shape of a circular arc and lie on a common circle about the rotational axis 12. This enables the locking pins 20, 21 which have been latched into the locking grooves 25, 26 to be swiveled.

[0036] The locking grooves 25, 26 have semicircular ends 27, 27′; 28, 28′, one of which is designed in each case per locking groove 25, 26 as a central stop 29, 30 for the locking pins 20, 21, for fixing the central position of the swiveling blades 7.

[0037] The central stops 29, 30 are arranged mirror-symmetrically to the central position of a swiveling blade 7, so that each central stop 29, 30 blocks a different swiveling direction of the internal rotor 2. It is therefore sufficient only to unlock one locking pin 20, 21 in order to pass from the central position of the swiveling blades to one of the end positions. The locking pin 20, 21 remaining in each case in the locking grooves 25, 26 has, in the end positions of the swiveling blades 7, sufficient space from those ends 28, 28′ of the locking grooves 25, 26 which are remote from the stop, in order to provide unambiguous stop positions.

[0038] In FIG. 3, the swiveling blades 7 bear against the trailing stops 19. The first locking pin 20 is situated outside the first locking groove 25 while the second locking pin 21 is arranged in the second locking groove 26 at a distance from its second semicircular end 28′ which is remote from the stop.

[0039] In FIG. 4, the swiveling blades 7 bear against the leading stops 18. The second locking pin 21 is situated outside the second locking groove 26 while the first locking pin 20 is arranged in the first locking groove 25 at a distance from its second semicircular end 28 which is remote from the stop.

[0040] The angular position of the central stops 29, 30 with respect to the leading and trailing stops 18, 19 can be set by rotation of the first side wall 10 with the locking grooves 25, 26 relative to the external rotor 1.

[0041] It emerges from FIG. 1 that the locking grooves 25, 26 have, at their groove bottom, oil channels 31, 32 which, for the unlatching of the locking pins 20, 21, are filled with compressed oil. The compressed oil passes via oil lines 33, 34 of the first side wall 10 from the working chambers 8, 9 into the locking grooves 25, 26.

[0042] During installation of the camshaft adjuster, the latter is locked completely in the base position. Since this does not, however, correspond to the “zero position” on the leading stop 18 of the swiveling blades 7, the differential angle between the central or base position and the leading stop 18 has to be as precise as possible for the resetting of the regulator. This differential angle has therefore been rendered adjustable.

[0043] The two locking pins 20, 21 are latched in place in the pre-assembled camshaft adjuster which has not yet been screwed together. The leading stop 18 of the external rotor 1 is then swiveled against the swiveling blades 7, which are locked in the central position. Swiveling of the external rotor 1 through the differential angle then takes place. Finally, the external rotor 1 and the side walls 10, 11 are screwed in place. If the trailing stop 19 is to be used for the resetting, then the differential angle is set between the central position and trailing stop by swiveling the external rotor 1.

[0044] The camshaft adjuster according to the invention functions as follows:

[0045] The internal combustion engine runs at low idling before it is shut off. The electronic regulator has consequently switched the control valve to be de-energized. As a result, the first working chamber 8 and the first locking groove 25 are charged with oil pressure, as a result of which the first locking pin 20 is unlocked and the swiveling blades 7 come to bear against the leading stop 18. The second locking pin 21 is situated outside the second locking groove 26, with the second working chamber 9 unpressurized. Said locking pin is prestressed by its compression spring 23.

[0046] With the internal combustion engine at a standstill, the oil pressure drops to zero, so that the first locking pin 20 latches into the first locking groove 25. As the internal combustion engine peters out, the swiveling blades 7 have swung into a swiveling position between the leading stop 18 and the base position while the second locking pin 21 is also arranged outside the second locking groove 26 and is prestressed by its compression spring 23.

[0047] When the internal combustion engine is started, the internal rotor 2 is adjusted toward “trailing” by the dragging torque of the camshaft until the first locking pin 20 in the first locking groove 25 comes against the first central stop 29. This enables the second locking pin 21 to be latched into the second central stop 30 of the second locking groove 26, so that the starting of the engine can take place with the central position of the swiveling blades 7 completely locked.

[0048] After starting of the engine has taken place, the regulator raises the oil pressure in the first oil pressure lines 14, the first working chambers 8 and the first locking groove 25. As a result, the first locking pin 20 is unlocked and the second locking pin 21 is kept in pressure contact with the second central stop 30.

[0049] In order to transfer to regulated operation, the regulator adjusts the swiveling blades 7 into the swiveling region in front of the trailing stop 19 by means of a higher pressure in the second working chambers 9 than the pressure in the first working chambers 8. As a result, the second locking pin 21 is also unlocked, so that the internal rotor 2 can move freely.

LIST OF REFERENCE NUMBERS

[0050]1 External rotor

[0051]2 Internal rotor

[0052]3 Partition

[0053]4 Hydraulic chamber

[0054]5 Hub

[0055]6 Slot

[0056]7 Swiveling blades

[0057]8 First working chamber

[0058]9 Second working chamber

[0059]10 First side wall

[0060]11 Second side wall

[0061]12 Rotational and swiveling axis

[0062]13 Tip

[0063]14 First compressed oil line

[0064]15 Second compressed oil line

[0065]16 First oil bore

[0066]17 Second oil bore

[0067]18 Leading stop

[0068]19 Trailing stop

[0069]20 First locking pin

[0070]21 Second locking pin

[0071]22 Axially parallel bore

[0072]23 Compression spring

[0073]24 Bearing cup

[0074]25 First locking groove

[0075]26 Second locking groove

[0076]27 First semicircular end

[0077]27′ First semicircular end

[0078]28 Second semicircular end

[0079]28′ Second semicircular end

[0080]29 First central stop

[0081]30 Second central stop

[0082]31 First oil channel

[0083]32 Second oil channel

[0084]33 First oil line

[0085]34 Second oil line 

1. A hydraulic camshaft adjuster for adjusting the angle of rotation of the camshaft of an internal combustion engine relative to its crankshaft, said camshaft adjuster having an external rotor (1) connected in a rotationally fixed manner to a driving wheel, and an internal rotor (2) connected in a rotationally fixed manner to the camshaft, the external rotor (1) having at least one hydraulic chamber (8) with radial partitions (3) and two side walls (10, 11), and the internal rotor (2) having a hub (5) with at least one swiveling blade (7) which divides the hydraulic chamber (4) into two working chambers (8, 9) in an oil-tight manner, it being possible for each swiveling blade (7) to be swiveled hydraulically between a trailing stop (19) and a leading stop (18) by an oil pressure which is controlled by an electronic regulator via a control valve, and each swiveling blade having, between the stops (18, 19), a base or central position which can be locked by two spring-loaded and hydraulically unlockable locking pins (20, 21), wherein the locking pins (20, 21) are preferably of identical design and are arranged in the hub (5) of the internal rotor (2) and parallel to its rotational axis (12) and can be latched into preferably identically designed locking grooves (25, 26) in at least one side wall (10, 11):
 2. The camshaft adjuster as claimed in claim 1, wherein the locking grooves (25, 26), which are designed in the shape of a circular arc, of the locking pins (20, 21) are arranged on a preferably common circle about the rotational axis (12) of the external and internal rotors (1, 2).
 3. The camshaft adjuster as claimed in claim 2, wherein the locking grooves (24, 26) have preferably semicircular ends (27, 27′ and 28, 28′) and are designed to be of a width which corresponds to the diameter of the locking pins (20, 21), which diameter is enlarged by a clearance to allow movement.
 4. The camshaft adjuster as claimed in claim 3, wherein one of the ends (27, 27′ and 28, 28′) of the two locking grooves (25, 26) is designed in each case as a central stop (29, 30) for the locking pins (20, 21), for fixing the central position of the swiveling blades (7).
 5. The camshaft adjuster as claimed in claim 4, wherein the central stops (29, 30) are arranged mirror-symmetrically, so that a different swiveling direction of the internal rotor (2) is blocked by each central stop (29, 30).
 6. The camshaft adjuster as claimed in claim 5, wherein the ends (27, 27′ and 28, 28′) of the two locking grooves (25, 26) are arranged, when the swiveling blades (7) bear against the leading stop or against the trailing stop (18, 19), at a distance from the locking pins (20, 21) which are each latched in place.
 7. The camshaft adjuster as claimed in claim 6, wherein the central stops (29, 30) can be set with respect to the leading and trailing stops (18, 19) by rotation of the first side wall (10), which is provided with the locking grooves (25, 26), relative to the external rotor (1).
 8. The camshaft adjuster as claimed in claim 7, wherein the locking grooves (25, 26) and their oil channels (31, 32) are flow-connected to the corresponding working chambers (8, 9) via oil lines (33, 34) which are preferably arranged in the first side wall (10).
 9. The camshaft adjuster as claimed in claim 1, wherein the locking grooves (25, 26) are in each case arranged separately in the two side walls (10, 11).
 10. A method for operating a hydraulic camshaft adjuster according to the preamble of claim 1, wherein the electrical regulator regulates the oil pressure in the working chambers (8, 9) during the shutting off and restarting of the internal combustion engine in such a way that, with the additional use of the dragging torque of the camshaft, the starting of the engine takes place from a base or central position of the swiveling blades (4), which position is locked by the two locking pins (20, 21).
 11. The method as claimed in claim 10, wherein at low idling of the internal combustion engine before it is shut off, the electrical regulator charges, via the control valve, the first working chamber (8) together with associated first locking groove (25) with oil pressure, as a result of which the first locking pin (20) is unlocked and the swiveling blades (7) come to bear against the leading stop (18) while the second locking pin (21), with the second working chamber (9) unpressurized, is situated outside the second locking groove (26) and is prestressed by its compression spring (23).
 12. The method as claimed in claim 11, wherein, with the internal combustion engine at a standstill and, as a result, an absence of oil pressure, the first locking pin (20) is latched in the first locking groove (25) and the swiveling blades (7) have a swiveling position between the leading stop (18) and the base position while the second locking pin (21) is also arranged outside the second locking groove (26) and is prestressed by its compression spring (23).
 13. The method as claimed in claim 12, wherein, when the internal combustion engine is started, the internal rotor (2) is adjusted to “trailing” by the dragging torque of the camshaft until the first locking pin (20) in the first locking groove (25) comes against the first central stop (29) and thereby-enables the second locking pin (21) to latch into the second central stop (30) of the second locking groove (26), so that the starting of the engine takes place with the central position completely locked.
 14. The method as claimed in claim 13, wherein, directly after starting of the engine has taken place, the regulator raises the oil pressure in the first oil pressure lines (14), the first working chambers (8) and the first locking groove (25), thereby unlocking the first locking pin (20) and keeping the second locking pin (21) in pressure contact with the second central stop (30).
 15. The method as claimed in claim 14, wherein, in order to transfer to regulated operation, the regulator adjusts the swiveling blades (7) into the region before the trailing stop (19), by means of a higher pressure in the second working chamber (9) than in the first working chamber (8), and thereby also unlocks the second locking pin (21), so that the internal rotor (2) can move freely. 